I think you are misconstruing the argument. I don't think Jon and others are saying that we should let people off because of "Peace and Lollipops". Rather that when you can achieve freedom peacefully with less deaths on both sides, this is better than continued death in the name of "justice".
For example let's say group A oppressed group B historically. If that oppression could be stopped with peaceful talks, resulting in only let's say 100 deaths on both sides, would you rather choose continued killing, resulting in 10,000 deaths on both sides in order to exact complete retribution for everything group A did?
I personally, am glad that even though Ireland was oppressed by Britain for around three hundred years, we don't plan on dealing out retribution until 2221. I know my grandparents generation did want that retribution to some degree, but I'm glad we didn't choose that road.